Bai giang pttkk drilling fluid circulation system

Drilling Fluid Circulation Systems Introduction Mud Pumps Duplex PDP & Triplex PDP Solids removal Solid Control Equipment 4.1 Shale shakers 4.2 Degasser 4.3 Mud Cleaners Treatment and Mixing Equipment References (CDF) Jorge H.B Sampaio Jr “Drilling Engineering Fundamentals.” Master of Petroleum Engineering Curtin University of Technology, 2007 Chapter 2 (WEC) Rabia, Hussain “Well Engineering & Construction” Entrac Consulting Limited, 2002 Chapter & 16 01/2018 Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com Introduction 01/2018 Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com Drilling Fluid Roles ✓ The drilling fluid plays several functions in the drilling process ✓ The most important are: ➢ clean the rock fragments from beneath the bit and carry them to surface ➢ exert sufficient hydrostatic pressure against the formation to prevent formation fluids from flowing into the well ➢ maintain stability of the borehole walls ➢ Cool and lubricate the drillstring and bit 01/2018 Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com Drilling Fluid Circulation ✓ Drilling fluid is forced to circulate in the hole ➢ at various pressures and ➢ flow rates ✓ Drilling fluid is stored in steel tanks located beside the rig ✓ Powerful pumps force the drilling fluid through surface high pressure connections to a set of valves called pump manifolds located at the derrick floor 01/2018 Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com Drilling Fluid Circulation (Cont) ✓ From the manifold, the fluid goes up the rig within a pipe called standpipe to approximately 1/3 of the height of the mast ✓ From there the drilling fluid flows through a flexible high pressure hose to the top of the drillstring ➢ The flexible hose allows the fluid to flow continuously as the drillstring moves up and down during normal drilling operations 01/2018 Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com Swivel ✓ The fluid enters in the drillstring through a special piece of equipment called swivel located at the top of the kelly ➢ The swivel permits rotating the drillstring while the fluid is pumped through the drillstring 01/2018 Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com Drilling Fluid in Wellbore ✓ In wellbore ➢ The drilling fluid then flows down the rotating drillstring and jets out through nozzles in the drill bit at the bottom of the hole ➢ The drilling fluid picks the rock cuttings generated by the drill bit action on the formation ➢ The drilling fluid then flows up the borehole through the annular space between the rotating drillstring and borehole wall 01/2018 Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com Drilling Fluid at Surface ✓ At surface ➢ At the top of the well (and above the tank level), the drilling fluid flows through the flow line to a series of screens called the shale shaker ❖ The shale shaker is designed to separate the cuttings from the drilling mud ❖ Other devices are also used to clean the drilling fluid before it flows back into the drilling fluid pits 01/2018 Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com Process of Mud Circulation ✓ The principal components of the mud circulation system are: ➢ Pits and tanks, ➢ Pumps, ➢ Flow line, ➢ Solids and contaminants removal equipment, ➢ Treatment and mixing equipment, ➢ Surface piping and valves, ➢ The drillstring 01/2018 Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com The Tanks ✓ The tanks (3 or – settling tank, mixing tank(s), suction tank) are made of steel sheet ➢ They contain a safe excess (neither too big nor too small) of the total volume of the borehole ❖ In the case of loss circulation, this excess will provide the well with drilling fluid while the corrective measures are taken ➢ The number of active tanks depends on ❖ The current depth of the hole (bypasses allow to isolate one or more tanks.) ➢ The tanks will allow enough retaining time so that much of the solids brought from the hole can be removed from the fluid 01/2018 Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com 10 Centrifugal Pumps ✓ This type uses an impeller ➢ for the movement of fluid ➢ rather than a piston reciprocating inside a cylinder ✓ Centrifugal pumps are used ➢ to supercharge mud pumps and ➢ providing fluid to solids control equipment and mud mixing equipment 01/2018 Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com 21 Duplex PDP & Triplex PDP 01/2018 Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com 22 Duplex vs Triplex Pumps ✓ A basic pump consists of a piston (the liner) reciprocating inside a cylinder ✓ A pump is described as single acting ➢ if it pumps fluid on the forward stroke (Triplex pumps) ✓ and double acting ➢ if it pumps fluid on both the forward and backward strokes (Duplex) 01/2018 Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com 23 Duplex Pumps 01/2018 Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com 24 Triplex Pumps 01/2018 Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com 25 Pump Liners ✓ Pump liners fit inside the pump cavity ➢ These affect the pressure rating and flow rate from the pump ➢ For a given pump, a liner has the same OD but with different internal diameters ➢ The smaller liner (small ID) is used in the deeper part of the well where low flow rate is required but at much higher operating pressure ✓ The size of the pump ➢ 01/2018 is determined by the length of its stroke and the size of the liner Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com 26 The Pump Factor ✓ The duplex mud pump consists of two doubleaction cylinders ➢ This means that drilling mud is pumped with the forward and backward movement of the barrel ➢ For a duplex pump (2 double-action cylinders) the 𝜋 pump factor is given by: 𝐹𝑝 = (2𝑑𝐿2 − 𝑑𝑅2 )𝐿𝑆 𝐸𝑉 ✓ The triplex mud pump consists of three singleaction cylinders ➢ This means that drilling mud is pumped only in the forward movement of the barrel ➢ For a triplex pump the pump factor is: 𝐹𝑝 = 01/2018 Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com 3𝜋 𝑑 𝐿 𝐸 𝐿 𝑆 𝑉 27 Volumetric Efficiency ✓ Drilling mud usually contain little air and is lightly compressible ➢ Hence the piston moves through a shorter stroke than theoretically possible before reaching discharge pressure ➢ As a result the volumetric efficiency is always less than one, typically 95% for triplex and 90% for duplex ✓ In addition due to power losses in drives ➢ The mechanical efficiency of most pumps is about 85% 01/2018 Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com 28 Pump Flow Rate ✓ For both types of PDP, the flow rate is calculated from: q = N Fp ✓ For N in strokes per minute (spm), dL, dR, and LS in inches, Fp in in3, and q in gallons per minute (gpm) we have: 𝑞= 𝑁 𝐹𝑝 231 ➢ Note that in this particular formulation, the volumetric efficiency of the pump is included in the pump factor 01/2018 Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com 29 Pump Operating Pressure ✓ The horse power requirements of the pump depends on the flow rate and the pressure ✓ The operating pressure depends on ➢ Flow rate, depth and size of hole, size of drillpipe and drillcollars, mud properties and size of nozzles used ✓ A full hydraulics program needs to be calculated to determine the pressure requirement of the pump 01/2018 Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com 30 Pump Power ✓ Pumps convert mechanical power into hydraulic power From the definition of power P=F v ✓ In its motion, ➢ The piston exerts a force [F] on the fluid that is equal to the pressure differential in the piston Δp times the area A of the piston, and ➢ The velocity v is equal to the flow rate q divided by the area A, that is: 𝑞 𝑃𝐻 = ∆𝑝 𝐴 = ∆𝑝 𝑞 𝐴 ❖ 01/2018 For PH in hp, p in psi, and q in gal/min (gpm) we have: ∆𝑝 𝑞 𝑃𝐻 = 1714.29 Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com 31 Pump Factor & Hydraulic Power ✓ Compute the pump factor in gallons per stroke and in barrels per stroke for a triplex pump having ➢ 5.5 in liners and ➢ 16 in stroke length, ➢ With a volumetric efficiency of 90% ✓ At N=76spm, the pressure differential between the input and the output of the pump is 2400 psi ➢ 01/2018 Calculate ❖ The hydraulic power transferred to the fluid, and ❖ The required mechanical power of the pump if Em is 78% Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com 32 Pump Factor & Hydraulic Power ✓ The pump factor (triplex pump) in in3 per stroke is: 3𝜋 3𝜋 𝐹𝑝 = 𝑑𝐿 𝐿𝑆 𝐸𝑉 = 𝑥 5.52 𝑥 16 𝑥 90% = 1026 𝑖𝑛3 4 ✓ Converting to gallons per stroke and to barrels per stroke gives: 1 𝐹𝑝 = 1026 𝑥 = 4.44𝑔𝑝𝑠 = 4.44 𝑥 = 0.1058𝑏𝑝𝑠 231 42 ✓ The flow rate at N = 76spm is: 𝑞 = 𝑁 𝐹𝑝 = 76𝑠𝑝𝑚 𝑥 4.44𝑔𝑝𝑠 = 337.44𝑔𝑝𝑚 ✓ The hydraulic power transferred to the fluid is: ∆𝑝 𝑞 2400𝑝𝑠𝑖 𝑥 337.44𝑔𝑝𝑚 𝑃𝐻 = = = 468ℎ𝑝 1714.29 1714.29 ✓ To calculate the mechanical power required by the pump we must consider the efficiencies: 𝑃𝐻 468ℎ𝑝 𝑃= = = 667ℎ𝑝 𝐸𝑉 𝐸𝑚 90% 𝑥 78% 01/2018 Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com 33 Surge Dampeners ✓ Due to the reciprocating action of the PDPs, the output flowrate of the pump presents a “pulsation” (caused by the changing speed of the pistons as they move along the liners) ➢ This pulsation is detrimental to the surface and downhole equipment (particularly with MWD pulse telemetry system) ➢ To decrease the pulsation, surge dampeners are used at the output of each pump 01/2018 Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com 34 Schematic of A Typical Surge Dampener ✓ A flexible diaphragm creates a chamber filled with nitrogen at high pressure ✓ The fluctuation of pressure is compensated by a change in the volume of the chamber ✓ A relief valve located in the pump discharge line prevents line rupture in case the pump is started against a closed valve 01/2018 Đinh Công Vĩnh Luân – MSc in Offshore Engineering Email: luandcv@gmail.com 35